The present invention relates generally to couplings for connecting two pipeline sections for conveying fluid therethrough, as in the refueling of one moving vehicle from another. More particularly, the invention relates to couplings of this general type having coupling elements which latch together automatically when brought into engagement, and which release automatically when subjected to a predetermined minimum tensile force.
Although fluid couplings of this type can be used in almost any application requiring the transportation of fluids, they are ideally suited for use in refueling operations, which require the pumping of fluid fuel from one moving vehicle to another, such as from one aircraft to another or from a ship to an aircraft. In such refueling operations, it is desirable that the coupling should automatically disconnect when subjected to a predetermined minimum tensile force. This feature not only provides a convenient means for terminating a refueling operation, but also avoids damage to the fluid-conveying lines and consequent loss of fuel on inadvertent separation of the vehicles. It is also preferable that couplings of this type include a "dry-break" feature, whereby each member of the coupling is automatically sealed on disconnection, to eliminate or minimize any loss of fuel.
Although a number of couplings having these general characteristics are to be found in the prior art, and although some of these may be generally satisfactory in some respects, none of them includes means for conveniently adjusting the minimum uncoupling force over wide limits. Ideally, couplings of this type should also be manually disconnectable and should, as far as possible, be pressure balanced, i.e., the minimum tensile force necessary to disconnect the coupling should be substantially independent of the fluid pressure inside the coupling. In addition, any self-sealing valves used to implement the dry-break feature should operate independently of the pressure balancing and tension break-away features so that the dry-break feature may be optionally dispensed with, without detracting from the other performance features of the coupling. The present invention satisfies all of these needs and requirements.